NPDP Dam Dictionary

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Term AKA Definition
Interstitial flow Portion of surface water that infiltrates the streambed and moves through pores in subsurface.
Intrusion A feature (landform, vegetation, or structure) that is generally considered out of context because of excessive contrast and disharmony with characteristic landscape.
Inundate To cover with impounded waters or floodwaters
Inundation map A map of the ground surfaces downstream of a dam showing the probable encroachment by water released because of failure of the dam or from abnormal flood flows released through a dam's spillway.
Invert The lowest point of an underground excavation or the lowest point of the interior of a circular conduit, pipe, or tunnel.
Invertebrates All animals without a vertebral column, e.g. spiders, crabs, or worms.
Ion An atom or molecule that has lost or gained one or more electron
Iowa vane A flow deflector that will divert water in a way calculated to attract fish.
Irretrievable Commitments that are lost for a period of time.
Irreversible Commitments that cannot be reversed, except perhaps in the extreme long term.
Irrigable acreage for service The acreage classified as irrigable for which works have been constructed and water is available. This figure may change from year to year, generally upward, as project works are completed and service is made available to additional acreage. Upon completion of the project, the irrigable acreage for service will equal the irrigable land as presented in the repayment contract or most recent project authorization. See irrigated acreage.
Irrigable land Arable land under a specific plan for which a water supply is or can be made available and which is provided with or planned to be provided with irrigation, drainage, flood protection, and other facilities as necessary for sustained irrigation.
Irrigated acreage The irrigable acreage actually irrigated in any one year. It will include irrigated crop land harvested, irrigated pasture, crop land planted but not harvested, and acreage in irrigated rotation used for soil-building crops.
Irrigation Act of supplying dry land with water in order to grow crops or other plants.
Jet-flow gate A gate consisting of a wheel-mounted leaf moved vertically by a motor-driven screw hoist.
Jetting A method of compacting soil using a hose or other device, with a high velocity stream of water, worked down through the depth of soil placed.
Jetty Pier or other structure built out into a body of water to influence the current or tide, or to protect a harbor or shoreline.
Joint See expansion joint, cold joint, construction joint, contraction joint, and control joint.
Joint use capacity The reservoir capacity assigned to flood control purposes during certain periods of the year and to conservation purposes during other periods of the year.
Juvenile salmon All early lifestages of downstream migrating salmon (fry through smolt).
Kilovolt kV One thousand volts.
Kilovolt-ampere kVA 1000 volt-amperes.
Kilowatt kW One thousand watts, or about 1.34 horsepower.
Kilowatt-hour kWh Basic unit of electric energy equal to an average of one kilowatt of power applied over one hour.
Lacustrine habitat Lake or reservoir wetland habitat.
Lagomorphs The order of mammals including rabbits, hares, and pikas.
Laminar flow The flow field can be characterized by layers of fluid, one layer not mixing with adjacent ones. The flow is laminar or turbulent depending on the value of the Reynolds number, which is a dimensionless ratio of the inertial forces to the viscous forces. In laminar flow, viscous forces are dominant and the Reynolds number is relatively small. In turbulent flow, the inertial forces are very much greater than the viscous forces and the Reynolds number is large. Laminar flow occurs very infrequently in open channel flow.
Land classification Reclamation's systematic placing of lands into classes based on their suitability for sustained irrigated farming. Land classes are defined by productivity, with class 1 being the most productive. For other classes, the equivalent acreage to class 1 for the same productivity is defined (class 1 equivalency). For example, (the productivity of) X acres of class 2 land is equal to (the productivity of) 1 acre of class 1 land.
Land ownership Land held in title
Land retirement Permanent removal of land from agricultural production.